The present invention relates to the fields of metal oxide reduction to metal powder through the use of a liquid metal reducing agent. It especially relates to the reduction of the oxides of reactive metals, such as titanium, hafnium and zirconium.
In the past the difficult to reduce oxides of the metals titanium, zirconium, thorium, uranium, vanadium, etc. have been reduced by a liquid metal reducing agent as described in U.S. Pat. Nos. 1,573,083; 1,704,257; 1,814,719; 2,446,062; 2,537,068; 2,653,869; and 2,707,679. While other reducing agents have been utilized liquid calcium has been typically preferred because of its oxide's very negative free energy of formation.
However the use of liquid calcium as a reducing agent has been limited to temperatures above 850.degree. C., the melting point of pure calcium. The actual reduction temperatures taught by previous investigators has ranged from approximately 900.degree. C. to 1350.degree. C. These high reduction temperatures in combination with localized high temperatures generated by the heat released by the reduction reaction itself have tended to cause agglomeration of the powders produced. These powder agglomerates are deleterious in that they can entrap calcium oxide, calcium and other impurities which are difficult to remove by the leaching techniques used to clean the metal powders.